The invention lies in the field of semiconductors. The present invention relates to a semiconductor module with a number of semiconductor chips that are respectively disposed on a chip carrier. At least some of the semiconductor chips are disposed one above another. The configuration of the semiconductor module can have only two chips, for example, that are disposed one above another in a stack construction. However, the semiconductor module can also include a row of semiconductor chips that are disposed alongside one another, a second row of semiconductor chips being disposed in a stack configuration above the first row of semiconductor chips. A number of semiconductor chips or a number of rows of semiconductor chips one above another is also conceivable. Between the semiconductor chips there are respective case conductive connections, which are formed by flexible tapes with appropriate conductor runs.
Semiconductor modules are disclosed in the prior art, for example, in R. Leutenbauer et al., xe2x80x9cDevelopment of a Top-Bottom BGAxe2x80x9d, HDI, December 1998, pages 28 to 32. The article discloses that semiconductor chips are fitted either on a polyimide substrate or a rigid substrate, and a flexible tape is provided as a conductive connection between the substrate parts, which respectively act as chip carriers. Folding up the corresponding structure produces the semiconductor module, the conductive connection from one semiconductor chip on the first plane to a semiconductor chip disposed above it on the second plane respectively being led around one side of the semiconductor chip on the first plane. However, such a configuration proves to be disadvantageous because, if the conductive connection is led around on one side, the line paths between the interconnected terminals of the semiconductor chips disposed above one another turn out to have different lengths. Differing lengths leads to different signal propagation times between the corresponding terminals and, therefore, to problems during signal processing. In addition, such a configuration cannot be used for all types of semiconductor chips. This is true, because, for example, for semiconductor chips with chip contact terminals in a mid-axis of the semiconductor chip, with which contact is made by a beam lead method, the substrate has to be configured to be interrupted in the area of the mid-axis. Thus, a conductive connection, at least to one half of the semiconductor chip on the first plane, and a conductive connection to at least one half of the semiconductor chip on the second plane, can hardly still be produced by a conductive connection on one side.
It is accordingly an object of the invention to provide a semiconductor module with a number of semiconductor chips and a conductive connection between the semiconductor chips by flexible tapes that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type, that provides a semiconductor module with a number of semiconductor chips in which all types of semiconductor chips can be used, and that has the smallest possible difference in the signal propagation times between the chip contact terminals.
With the foregoing and other objects in view, in a semiconductor module of the type having a chip carrier and semiconductor chips disposed on the chip carrier, at least a second subset of the semiconductor chips to be disposed above a first subset of the semiconductor chips, the first subset having a contacting side and mutually opposing side faces, there is provided, in accordance with the invention, an improvement, including flexible tapes forming conductive connections between the first subset of semiconductor chips and the second subset of semiconductor chips, two of the flexible tapes originating from the first subset and leading to the second subset, the two of the flexible tapes respectively extending from a contacting side of the first subset around respective side faces of the first subset to the second subset.
In the improvement, two flexible tapes originating from the first subset of semiconductor chips lead to the second subset of semiconductor chips, the flexible tapes extending from a contact-making side of the first subset of semiconductor chips around respective mutually opposite side faces of these semiconductor chips to the second subset of semiconductor chips. In principle, however, more than two planes of semiconductor chips can be disposed one above another. For clarity, the present invention will be described using two planes of semiconductor chips.
The advantage of such a configuration is that the signal propagation times between the chip contact terminals of the semiconductor chips disposed one above another can be shortened significantly because the conductor runs are led around one of the two side faces of the semiconductor chips of the first plane. In addition, the problems of producing a conductive connection between the semiconductor chips are overcome. Such problems arise when the chip carrier has to have an interrupted configuration because of the configuration of the chip contact terminals, in order, for example, to be able to implement the making of contact through beam leads.
The chip carriers of the individual semiconductor chips can in principle be configured in any desired way. In a first development of the invention, the chip carrier of the first subset of semiconductor chips is a flexible tape. The tape includes both the chip carrier of the first subset of semiconductor chips and the conductive connections to the second subset of semiconductor chips around the side faces of the first subset of semiconductor chips. Thus, the semiconductor chips of the first plane can be disposed on a continuous tape, whose ends project on both sides of the semiconductor chip. After the first subset of semiconductor chips has been mounted on the flexible tape, the projecting ends can then be folded around the side faces of the semiconductor chip to produce a conductive connection to the semiconductor chips disposed above them.
In a further embodiment of the invention, the second subset of semiconductor chips is disposed on a separate chip carrier. The second plane of semiconductor chips can then be disposed above the first plane of semiconductor chips and, subsequently, by folding the projecting ends around the side faces of the first plane of semiconductor chips, a conductive connection to the second plane of semiconductor chips is produced.
In an alternative embodiment, the chip carrier of the first subset of semiconductor chips can also form the chip carrier of the second subset of semiconductor chips. As such, the chip carrier is configured as a continuous tape. Following the mounting of the first subset of semiconductor chips on the flexible tape, a projecting end remaining free on one side and on the other side of these semiconductor chips, the second subset of semiconductor chips can be mounted on the flexible tape at a certain distance. By folding up the entire configuration, the second subset of semiconductor chips can then be disposed in a stack configuration above the first subset of semiconductor chips, a first conductive connection between the two planes of semiconductor chips automatically being folded around the side faces of the semiconductor chips of the first plane. In order to produce the second conductive connection between the semiconductor chips, only the free, projecting end of the flexible tape is folded around the other side face of the semiconductor chips of the first plane, and conductively connected to the semiconductor chips of the second plane.
A development of the invention provides that a respective side of a semiconductor chip of the first subset opposite the contact-making side of the first subset adjoins a corresponding side of a semiconductor chip of the second subset opposite its contact-making side. Therefore, the semiconductor chips are disposed xe2x80x9cback to back.xe2x80x9d As such, a flexible tape can be disposed around the entire module configuration as a chip carrier or conductive connection, which on one hand makes it easier to make contact with the semiconductor chips and, on the other hand, constitutes a protection for the entire module configuration, for example against mechanical influences.
The semiconductor chips can, in particular, be configured to provide chip contact terminals in a mid-axis of the contact making side of the semiconductor chips. The chip contact terminals are used to produce a conductive connection between the semiconductor chips and the respective chip carrier. The conductive connection can, in particular, be produced by a beam lead contacter.
In accordance with a concomitant feature of the invention, and, in order to make contact with the entire semiconductor module, module contact terminals can be provided on one side of the semiconductor module. These terminals can be disposed, for example, in the area of the contact-making side of the first subset of semiconductor chips. The module contact terminals are then connected to the corresponding chip contact terminals of the semiconductor chips through appropriate conductor runs on the chip carriers and by the conductive connections between the semiconductor chips and chip carriers. The module contact terminals can, for example, be configured as solder beads or pins.
Other features that are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a semiconductor module with a number of semiconductor chips and a conductive connection by flexible tapes between the semiconductor chips, it is nevertheless not intended to be limited to the details shown because various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.